To determine the phylogenetic relationship between sugarcane cultivars and other members of the Saccharinae subtribe, we identified the fast evolving ITS1-5.8S-ITS2 (ITS = internal transcribed spacer; 5.8S = 5.8S ribosomal DNA) region of the sugarcane genome in the Sugarcane Expressed Sequence Tag (SUCEST) genome project database. Parsimony analysis utilizing this region and homologs belonging to the 23 closely related Andropogoneae currently deposited in the GenBank database has shown sugarcane as the sister group of Saccharum sinense. However, because there are few parsimony-informative characters and high homoplasy in the ITS1-5.8S-ITS2 region we were not able to determine with confidence the phylogenetic relationship between sugarcane and some of the remaining members of Saccharine subtribe. To find alternatives for the phylogenetic reconstruction of sugarcane evolutionary history, we selected 17 markers (nuclear, chloroplastic or mitochondrial) from the SUCEST database of which apha-tubulin, ribosomal protein L16 (rpl16) and DNA-directed RNA polymerase beta chain (rpoC2) were found to have a low incidence of polymorphism and comparable, or even faster, rates of evolution than the ITS1-5.8S-ITS2 region. We suggest that these markers should be considered as preferential choices for phylogenetic studies of Saccharinae subtribe.
